The Vesper Holly series follows established precedents in literary tradition. In all five books, Alexander uses the mystery pattern set by Conan Doyle in the most famous of all Victorian mystery series, Sherlock Holmes.

Like Holmes, Vesper solves mysteries with her powers of observation and her intellect. As Holmes is challenged by that Napoleon of crime, Professor Moriarty, so is Vesper challenged by Dr. Helvitius. Like Watson, her guardian Brinnie is the first-person naive narrator of the adventures. Because Alexander employs a naive narrator, he is able to drop clues, build suspense, and amuse the reader at the same time.

Much of the humor in all the Vesper Holly books comes from Brinnie's understatement and stilted language. For example, in The El Dorado Adventure, while being kidnapped, Brinnie worries about hygiene: One of the ruffians had thrust Vesper's bandanna into her mouth.